High-temperature-resistant protective layer as well as preparation method and application thereof

Abstract

The invention relates to a high-temperature-resistant protective layer and a preparation method and application thereof. The high-temperature-resistant protective layer is prepared from the following components in parts by weight: 100 parts of a monomer A; 7-19 parts of a filler; 2-8 parts of a catalyst; 5-11 parts of an acid; 48 to 77 parts of water; the high-temperature-resistant protective layer is printed on the surface of the carbon-containing electric heating material in a silk-screen printing mode, then baking forming is conducted at the temperature of 50-70 DEG C, and the high-temperature-resistant protective layer can be obtained on the surface of the carbon-containing electric heating material after cooling. Compared with the prior art, the carbon-containing electric heating material can be effectively isolated from air through the high-temperature-resistant protective layer, carbon-containing components in the electric heating material are prevented from being oxidized by the air, and the carbon-containing electric heating material protected by the high-temperature-resistant protective layer stably operates at the working temperature of 500 DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and in particular relates to a high temperature resistant protective layer and a preparation method and application thereof. Background Art

[0002] With the development of electric heating technology, carbon-containing electric heating materials, including graphene electric heating materials and carbon ceramic electric heating materials, have gradually replaced traditional resistance wire heaters and ceramic PTC heaters in the field of low-temperature heating due to their large heating area and uniform temperature. However, in the field of high-temperature heating, carbon-containing electric heating materials still need to solve the problem of how to isolate them from oxygen. Unlike resistance wire heaters and ceramic PTC heaters, long-term contact with air of carbon-containing electric heating materials will cause oxidation of carbon atoms inside the material, reducing the power of such heaters and eventually losing their heating function.

[0003] In the field of low-temperature heating, using film materials such as PET or PI to encapsulate carbon-containing electric heating materials is a mature technical solution. In this way, the electric heating materials can be isolated from the air for protection; and because the heating temperature is low, the oxidation rate of carbon atoms is extremely slow, so the problem of oxidation is not obvious. However, when the carbon-containing electric heating materials are heated at a temperature higher than 150°C, film materials such as PET or PI will soften and are no longer suitable. If the electric heating material is directly exposed to the air, the oxidation rate of the carbon-containing components therein will increase exponentially with the increase in temperature, and this type of electric heating material will quickly lose its heating function; when the temperature exceeds 450°C, the carbon-containing components in the electric heating material will even burn directly.

[0004] Patents CN 216491110 U, CN 213342723 U and CN 113973406 use hot melt adhesive or organic silicone as a protective layer to isolate carbon-containing electric heating materials from the air. However, none of the above-mentioned prior arts mentions the limiting operating temperature of the heating element; on the other hand, the stable operating temperature of hot melt adhesive and organic silicone is less than 300°C. When this temperature is exceeded, these two types of adhesives will melt or even carbonize. Therefore, it can be reasonably inferred that their operating temperature cannot exceed 300°C. Patent CN114891389 A uses commercial coating as a protective layer, but the application also does not mention the limiting operating temperature of the heating element.

[0005] In order to protect carbon-containing electric heating materials under high-temperature heating working conditions, isolate them from the air and ensure stable operation, the protective layer material needs to have the following four characteristics at the same time: high temperature resistance, able to remain stable under high temperature conditions; temperature change resistance, able to withstand drastic temperature changes; good isolation effect, able to effectively isolate the air in a high-temperature environment; and sufficient mechanical strength, especially in a long-term high-temperature environment.

[0006] However, there is currently no suitable material that can be used as a protective layer for carbon-containing electric heating materials under high temperature heating conditions exceeding 300° C. Therefore, it is urgent to develop a high temperature resistant protective layer that can be used as a carbon-containing electric heating material under high temperature heating conditions. Summary of the invention

[0007] The purpose of the present invention is to provide a high temperature resistant protective layer and a preparation method and application thereof in order to realize the operation of carbon-containing electric heating materials under high temperature conditions.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] The present invention provides a high temperature resistant protective layer, which is made of the following components in parts by weight: 100 parts of monomer A, 7-19 parts of filler, 2-8 parts of catalyst, 5-11 parts of acid, and 48-77 parts of water;

[0010] The monomer A is 1-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid, and its structural formula is:

[0011]

[0012] The high temperature resistant protective layer is a mesh polymer structure, and its structural formula is:

[0013]

[0014] Wherein, R is -COOH.

[0015] The structure of the monomer A and polymer high temperature resistant protective layer of the present invention has the following characteristics:

[0016] (1) There is a benzyl group on each monomer A molecule. The carbon atom on the benzyl group will form a carbon atom free radical under the oxidation of the catalyst. The free radical will attack the carbon atom at the β position of the carbonyl group and the carbon atom at the para position of the N atom on the phenyl group, finally forming a spatial network structure.

[0017] (2) The monomer A molecule contains a hydrophilic carboxyl group, so the solubility of monomer A in water is good, which is convenient for adjusting the viscosity of the protective layer precursor and facilitating screen printing.

[0018] (3) The formed polymer molecules contain a large number of carboxyl groups. The H atoms and O atoms on this group can form hydrogen bonds with the carbon-containing electric heating material and the substrate to increase the adhesion.

[0019] (4) The pore structure of the formed polymer contains non-polar phenyl groups and polar carboxyl and carbonyl groups, which allows the filler molecules to be evenly dispersed in its pores, so there is no need to add additional dispersants.

[0020] (5) The formed polymer has large pores that can accommodate fillers, so it has good high temperature resistance, which facilitates its application in various scenarios.

[0021] Furthermore, the filler includes any one or more of aluminum oxide, magnesium oxide or mica powder. The filler is used in the present invention to improve the high temperature resistance of the protective layer after drying.

[0022] Furthermore, the catalyst is 9-thioxanthone. Thioxanthone catalysts are common photocatalysts that can catalyze a variety of photochemical reactions. In the present invention, 9-thioxanthone forms hydrogen bonds with acids, and enters an excited state after being irradiated by natural light or light to generate an excited intermediate; the excited catalyst has strong oxidizing properties, and can capture electrons from the benzyl carbon atom in monomer A to form a benzyl free radical intermediate, and then the benzyl free radical intermediate will attack the carbon atom at the β position of the carbonyl group; in a heating environment, this process will be greatly accelerated, and a polymer with a three-dimensional structure will eventually be generated.

[0023] Furthermore, the acid is trifluoromethanesulfonic acid. A trace amount of acid can provide an acidic environment and increase the reaction rate.

[0024] The present invention also provides a method for preparing a high temperature resistant protective layer, comprising the following steps:

[0025] S1: Add monomer A into water and disperse evenly;

[0026] S2: Add the filler into the solution of S1 and disperse it evenly;

[0027] S3: When stirring until there is no particulate matter, add a catalyst and an acid in sequence, and stir in the dark to obtain a high temperature resistant protective layer precursor;

[0028] S4: heat-treating the high temperature resistant protective layer precursor to obtain the high temperature resistant protective layer.

[0029] Furthermore, in step S1, the dispersion is performed by a disperser at a dispersion speed of 450-700 rpm.

[0030] Furthermore, in step S2, the dispersion speed is 500-900 rpm.

[0031] Furthermore, in step S3, the stirring speed is 1000-1500 rpm.

[0032] Furthermore, in step S4, the temperature of the heat treatment is 50-70°C.

[0033] The present invention also provides an application of a high-temperature resistant protective layer in protecting carbon-containing electric heating materials. The high-temperature resistant protective layer is prepared by screen printing a high-temperature resistant protective layer precursor on the surface of the carbon-containing electric heating material, and then baking and forming the layer at 50-70°C. After cooling, the high-temperature resistant protective layer can be obtained on the surface of the carbon-containing electric heating material.

[0034] Furthermore, the screen printing uses a 60-mesh screen.

[0035] Furthermore, the thickness of the carbon-containing electric heating material does not exceed 0.3 mm.

[0036] Furthermore, the baking time is 0.5-1h.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention prints a high temperature resistant protective layer precursor on the surface of a carbon-containing electric heating material by screen printing. After drying, the carbon-containing electric heating material can be effectively isolated from the air, thereby preventing the carbon-containing components in the electric heating material from being oxidized by the air, thereby extending the service life of the electric heating material, and allowing the carbon-containing electric heating material protected by the layer to operate stably at a working temperature of 500°C.

[0039] (2) The high temperature resistant protective layer monomer A of the present invention has a hydrophilic carboxyl group, which makes it more soluble in water, facilitates the adjustment of the viscosity of the protective layer precursor, and facilitates screen printing; the polymer molecules finally obtained by polymerization contain a large number of carboxyl groups, and the H atoms and O atoms on the group can form hydrogen bonds with the carbon-containing electric heating material and the substrate to increase the adhesion.

[0040] (3) The high temperature resistant protective layer of the present invention is a spatial network structure with a relatively large pore structure. The pore structure contains non-polar phenyl groups and polar carboxyl groups and carbonyl groups, so that the filler can be evenly dispersed in the pores. Therefore, no additional dispersant is required. In addition, the layer has good high temperature resistance, which facilitates its application in various scenarios of carbon-containing electric heating materials.

[0041] (4) The high temperature resistant protective layer precursor slurry of the present invention is easy to prepare and can be printed on the surface of the carbon-containing electric heating material by screen printing, which is simple to operate and convenient for large-scale industrial preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a physical photo of the high temperature resistant protective layer of Example 1 of the present invention after high temperature testing.

[0043] Figure 2 This is a photograph of the high temperature resistant protective layer of Example 3 of the present invention under infrared light.

[0044] Figure 3This is a physical photograph of the protective layer of Comparative Example 1 of the present invention after high temperature testing. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0046] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0047] The carbon-containing electric heating material of the present invention includes but is not limited to graphite, graphene, carbon fiber, carbon nanotube, carbon black, carbon ceramic electric heating material, etc. In the following embodiments and comparative examples, WJ-1103GF graphene heating oil of Hefei Microcrystalline Material Technology Co., Ltd. can be specifically selected, and its thickness is about 0.2 mm.

[0048] In the following examples and comparative examples, each weight portion of various raw materials is 10 grams.

[0049] In the following examples and comparative examples, the synthesis method and NMR data of monomer A are as follows:

[0050]

[0051] S1: Synthesis of dimethyl 2-((phenylamino)methylene)malonate (3):

[0052] Aniline (30.0 mmol) and dimethyl 2-methylenemalonate (35.0 mmol) were added to THF (200 mL) and stirred for 5 minutes in an oxygen atmosphere. Palladium acetate (1.5 mmol) and lithium bromide (10.0 mmol) were then added to the mixture. The mixture was heated and stirred for 5 hours in an oxygen atmosphere at 80° C. After cooling, it was extracted three times with water and ethyl acetate, and the organic phases were combined and spin-dried to obtain a crude product 3.

[0053] S2: Synthesis of dimethyl 2-((benzyl(phenyl)amino)methylene)malonate (4):

[0054] The crude product 3 (10.0 mmol), benzyl bromide (10.0 mmol), K2CO3 (12.0 mmol) and acetonitrile (50.0 mL) were mixed and stirred at 65°C for 8 hours. After the reaction was completed, the mixture was cooled to room temperature and evaporated under reduced pressure to obtain the crude product 4.

[0055] S3: Synthesis of 2-((phenyl(phenyl)amino)methylene)malonic acid (5):

[0056] The crude product 4 (8.0 mmol), NaOH (0.5 mmol), water (6 mL) and tetrahydrofuran (18 mL) were mixed. The mixture was heated to reflux at 70°C for 10 hours. After the reaction was completed, the mixture was cooled to room temperature, extracted with water and ethyl acetate three times, and the organic phases were combined. The organic phases were combined and dried to obtain the crude product 5.

[0057] S4: Synthesis of 3-(benzyl(phenyl)amino)-2-(chlorocarbonyl)acrylic acid (6):

[0058] The crude product 5 (7.5 mmol) was mixed with tetrahydrofuran (15 mL), and the mixture was stirred in an ice bath for 10 minutes. Oxalyl chloride (1.9 mmol) was slowly added to the mixture, and the mixture was stirred in an ice bath for 2 hours. After the reaction was completed, the mixture was evaporated under reduced pressure to obtain the crude product 6.

[0059] S5: Synthesis of 1-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (A):

[0060] The crude product 6 (5.0 mmol), acetonitrile (15 mL) and tetrahydrofuran (15 mL) were mixed and stirred at 0°C for 5 minutes. Ferric chloride (0.05 mmol) was added to the mixture and stirred at room temperature for 24 hours. After the reaction was completed, the mixture was evaporated under reduced pressure, and the crude product was purified by silica gel column chromatography (PE / EtOAc=2:1) ​​to obtain monomer A.

[0061] 1 H NMR (400MHz, DMSO-d6): δ15.12(s,1H),9.28(s,1H),8.39(d,J=8.0Hz,1H),7.97-7.86(m,2H),7.65(t,J=7.9Hz,1H),7.40-7.22(m,5H),5.87(s,2H); 13 CNMR (100MHz, DMSO-d6): δ177.9,166.1,150.3,139.5,134.1,129.0,128.8,128.1,126.7,126.0,118.6,110.3,56.4.

[0062] In the following examples, the chemical reaction equation of monomer A after heat treatment is as follows:

[0063]

[0064] The molecular structure of the network polymer finally obtained on the surface of the carbon-containing electric heating material is:

[0065]

[0066] Wherein, R is -COOH.

[0067] Embodiment 1:

[0068] The present embodiment provides a high temperature resistant protective layer and its specific application in carbon-containing electric heating materials. The high temperature resistant protective layer of the present embodiment comprises the following raw materials by weight: 100 parts of monomer A, 12 parts of aluminum oxide, 5.1 parts of 9-thioxanthone, 7.2 parts of trifluoromethanesulfonic acid, and 61 parts of water.

[0069] At room temperature, monomer A was added into water and stirred for 20 minutes at a disperser speed of 500 rpm; aluminum oxide was added into the solution in batches and dispersed at a disperser speed of 750 rpm; after all the monomers were added, the disperser speed was increased to 1250 rpm and stirred for 1 hour until the surface of the slurry was uniform and free of particulate matter; a catalyst and an acid were added and stirred for 5 minutes in a dark environment; the obtained viscous slurry was the protective layer material precursor of Example 1.

[0070] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing (the printing equipment is the TX-5080SF-P screen printer of Hangzhou Taoxing Printing Equipment Co., Ltd.), and the screen used is 60 mesh. After printing, it is baked in a blast oven at 55°C for 0.8 hours, taken out and cooled to room temperature, and the carbon-containing electric heating material with a high temperature resistant protective layer can be obtained.

[0071] Embodiment 2:

[0072] The present embodiment provides a high temperature resistant protective layer and its specific application in carbon-containing electric heating materials. The high temperature resistant protective layer of the present embodiment comprises the following raw materials by weight: 100 parts of monomer A, 9 parts of aluminum oxide, 6.3 parts of 9-thioxanthone, 8.7 parts of trifluoromethanesulfonic acid, and 58 parts of water.

[0073] At room temperature, monomer A was added into water and stirred for 20 minutes at a disperser speed of 680 rpm; aluminum oxide was added into the solution in batches and dispersed at a disperser speed of 660 rpm; after all the monomers were added, the disperser speed was increased to 1190 rpm and stirred for 1 hour until the surface of the slurry was uniform and free of particulate matter; a catalyst and an acid were added and stirred for 5 minutes in a dark environment; the obtained viscous slurry was the protective layer material precursor of Example 2.

[0074] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing, and the screen used is 60 mesh. After printing, it is baked in a blast oven at 55°C for 0.7 hours, taken out and cooled to room temperature, and the carbon-containing electric heating material with a high temperature resistant protective layer can be obtained.

[0075] Embodiment 3:

[0076] The present embodiment provides a high temperature resistant protective layer and its specific application in carbon-containing electric heating materials. The high temperature resistant protective layer of the present embodiment comprises the following raw materials by weight: 100 parts of monomer A, 19 parts of mica powder, 3.5 parts of 9-thioxanthone, 6.7 parts of trifluoromethanesulfonic acid, and 70 parts of water.

[0077] At room temperature, monomer A was added into water and stirred for 20 minutes at a disperser speed of 500 rpm; aluminum oxide was added into the solution in batches and dispersed at a disperser speed of 760 rpm; after all the monomers were added, the disperser speed was increased to 1250 rpm and stirred for 1 hour until the surface of the slurry was uniform and free of particulate matter; a catalyst and an acid were added and stirred for 5 minutes in a dark environment; the obtained viscous slurry was the protective layer material precursor of Example 3.

[0078] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing, and the screen used is 60 mesh. After printing, it is baked in a blast oven at 55°C for 0.9 hours, taken out and cooled to room temperature, and the carbon-containing electric heating material with a high temperature resistant protective layer can be obtained.

[0079] Embodiment 4:

[0080] The present embodiment provides a high temperature resistant protective layer and its specific application in carbon-containing electric heating materials. The high temperature resistant protective layer of the present embodiment comprises the following raw materials by weight: 100 parts of monomer A, 11 parts of mica powder, 7.5 parts of 9-thioxanthone, 6 parts of trifluoromethanesulfonic acid, and 59 parts of water.

[0081] At room temperature, monomer A was added into water and stirred for 20 minutes at a disperser speed of 640 rpm; aluminum oxide was added into the solution in batches and dispersed at a disperser speed of 880 rpm; after all the monomers were added, the disperser speed was increased to 1370 rpm and stirred for 1 hour until the surface of the slurry was uniform and free of particulate matter; a catalyst and an acid were added and stirred for 5 minutes in a dark environment; the obtained viscous slurry was the protective layer material precursor of Example 4.

[0082] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing, and the screen used is 60 mesh. After printing, it is baked in a blast oven at 55°C for 0.5 hours, taken out and cooled to room temperature, and the carbon-containing electric heating material with a high temperature resistant protective layer can be obtained.

[0083] Embodiment 5:

[0084] The present embodiment provides a high temperature resistant protective layer and its specific application in carbon-containing electric heating materials. The high temperature resistant protective layer of the present embodiment comprises the following raw materials by weight: 100 parts of monomer A, 17 parts of magnesium oxide, 6.8 parts of 9-thioxanthone, 8.4 parts of trifluoromethanesulfonic acid, and 57 parts of water.

[0085] At room temperature, monomer A was added into water and stirred for 20 minutes at a disperser speed of 490 rpm; aluminum oxide was added into the solution in batches and dispersed at a disperser speed of 660 rpm; after all the monomers were added, the disperser speed was increased to 1400 rpm and stirred for 1 hour until the surface of the slurry was uniform and free of particulate matter; a catalyst and an acid were added and stirred for 5 minutes in a dark environment; the obtained viscous slurry was the protective layer material precursor of Example 5.

[0086] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing, and the screen used is 60 mesh. After printing, it is baked in a blast oven at 55°C for 0.8 hours, taken out and cooled to room temperature, and the carbon-containing electric heating material with a high temperature resistant protective layer can be obtained.

[0087] Comparative Example 1:

[0088] The raw material formula and preparation steps of the protective layer of this comparative example are the same as those of Example 1, except that no acid is added.

[0089] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing. After printing, it is baked in a blast oven at 55°C for 0.8 hours, taken out and cooled to room temperature to obtain Comparative Example 1.

[0090] Comparative Example 2:

[0091] The raw material formula and preparation steps of the protective layer of this comparative example are the same as those of Example 2, except that the amount of aluminum oxide used is 30 parts.

[0092] The application steps are as follows: before printing, the protective layer material precursor needs to be stirred evenly in the dark, and then printed on the surface of the carbon-containing electric heating material by screen printing. After printing, it is baked in a blast oven at 55°C for 0.7 hours, taken out and cooled to room temperature to obtain Comparative Example 2.

[0093] The feeding amounts of the above embodiments and comparative examples are shown in Table 1, and the mass of each raw material is 10 grams.

[0094] Table 1 Summary of the feeding amounts of each embodiment and comparative example

[0095]

[0096] The present invention performs appearance and high temperature resistance tests on the above-mentioned embodiments and comparative examples. The test contents and methods are shown in Table 2, and the test results are shown in Table 3.

[0097] Table 2 Test content and test method

[0098] project Performance Indicators Test Method Appearance The surface color is uniform and there is no shedding Visual High temperature resistance No cracking at 500℃ Keep at 500℃ for 24 hours

[0099] Table 3 Summary of test results of various embodiments and comparative examples

[0100]

[0101] It can be seen from the above results that Examples 1-5 can meet the requirements of appearance and resistance to high temperature of 500°C. Figure 1 This is a real picture of the high temperature resistant protective layer of Example 1 after being kept at 500° C. for 24 hours. It can be seen that the surface of the protective layer is uniform without fine lines or cracks. Figure 2 This is a photo of the high temperature resistant protective layer of Example 3 under infrared light. It can be seen that Example 3 can remain stable at 500°C, and the heat transfer is uniform without obvious low temperature areas.

[0102] In Comparative Example 1, due to the lack of acid addition, the reaction is incomplete, and polymer molecules with a large enough molecular weight cannot be formed. The filler cannot be evenly dispersed in the pores of the polymer molecules. The protective layer precursor has a large fluidity, so the filler is unevenly distributed on the surface. After a period of time in a high temperature environment, the protective layer cracks (such as Figure 3 shown).

[0103] In Comparative Example 2, due to the excessive amount of filler added, the pore capacity was exceeded, and the excess filler aggregated on the surface of the cured protective layer. In addition, in a high temperature environment, the thermal expansion coefficients of the aggregated part and other parts were different, which eventually led to rapid cracking of the protective layer.

[0104] In summary, in order to protect carbon-containing electric heating materials in a high-temperature environment, isolate the air, and prevent the carbon-containing components in the electric heating materials from being oxidized by the air, the present invention has developed a high-temperature resistant protective layer material. The high-temperature resistant protective layer can enable the carbon-containing electric heating material protected thereby to operate stably at a working temperature of 500°C. The protective layer precursor is screen-printed on the surface of the carbon-containing electric heating material, and after drying, the carbon-containing electric heating material can be effectively isolated from the air, preventing the carbon-containing components in the electric heating material from being oxidized by the air, thereby extending the service life of the electric heating material; and the protective layer material has excellent resistance to high temperatures and drastic temperature changes, and is therefore very suitable as a high-temperature resistant protective layer for a type of carbon-containing electric heating material.

[0105] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A high temperature resistant protective layer, characterized in that: The high temperature resistant protective layer is made of the following components in parts by weight: 100 parts of monomer A, 7-19 parts of filler, 2-8 parts of catalyst, 5-11 parts of acid, and 48-77 parts of water; The structural formula of the monomer A is:

2. A high temperature resistant protective layer according to claim 1, characterized in that: The high temperature resistant protective layer is a mesh polymer structure, and its structural formula is: Wherein, R is -COOH.

3. A high temperature resistant protective layer according to claim 1, characterized in that: The filler includes any one or more of aluminum oxide, magnesium oxide or mica powder.

4. A high temperature resistant protective layer according to claim 1, characterized in that: The catalyst is 9-thioxanthone.

5. The high temperature resistant protective layer according to claim 1, characterized in that: The acid is trifluoromethanesulfonic acid.

6. A method for preparing the high temperature resistant protective layer according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: Add monomer A into water and disperse evenly; S2: Add the filler into the solution of S1 and disperse it evenly; S3: When stirring until there is no particulate matter, add a catalyst and an acid in sequence, and stir in the dark to obtain a high temperature resistant protective layer precursor; S4: heat-treating the high temperature resistant protective layer precursor to obtain the high temperature resistant protective layer.

7. The method for preparing a high temperature resistant protective layer according to claim 6, characterized in that: In step S1, the dispersion is performed by a disperser at a speed of 450-700 rpm; In step S2, the dispersion speed is 500-900 rpm; In step S3, the stirring speed is 1000-1500 rpm; In step S4, the temperature of the heat treatment is 50-70°C.

8. Use of the high temperature resistant protective layer according to any one of claims 1 to 5 in protecting carbon-containing electric heating materials, characterized in that: The high temperature resistant protective layer is printed on the surface of the carbon-containing electric heating material by screen printing, and then baked at 50-70°C to form the high temperature resistant protective layer. After cooling, the high temperature resistant protective layer can be obtained on the surface of the carbon-containing electric heating material.

9. The use of a high temperature resistant protective layer according to claim 8 in protecting carbon-containing electric heating materials, characterized in that: The screen plate used for the screen printing is 60 mesh, and the thickness of the carbon-containing electric heating material does not exceed 0.3 mm.

10. The use of a high temperature resistant protective layer according to claim 8 in protecting carbon-containing electric heating materials, characterized in that: The baking time is 0.5-1h.

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